It depends on the genre, the audience, and the publisher. Different ones have different standards. For instance, a book for kids probably won't have anything more graphic than maybe a kiss or something, while a romance publisher might say that they don't want anything showing an explicit act. It all depends, unfortunately.

Still, I do think that you probably shouldn't be too graphic, obviously; there is a point where, if you describe sex too graphically, it stops being a story and becomes porn or erotica. It can also be distracting, depending on how you write, too.

What kind of affair is it? Is it one that is more love based? Is it 'sex only' based?

I would think the type off affair drives the kind of style you are going to write and the detail needed to communicate how the sex in that affair works. If it is only about sex, then detailing specifics about the act seem more germane. If it is about love, then you can, I think, rely more on flowery, representative prose.

I think the best way to handle it is to imagine the completed scene then think if it would crop up in a BBC drama or something, is it alright for 9 oclock oclock viewing.

Usually highly detailed descriptions of anatomy and specifics on acts tend to breach into the world of erotica, but more vague descriptions work to which ever genre your writing in. Although I've read some fantasy books that didnt pull any punches, Anita Blake vampire hunter I was pretty sure was a horror/supernatural/crime series after the first few books, then it became something more.

At the end of the day go where the story takes you, if it demands high descriptions then don't scrim, a crime novel with one or two graphic sex scenes is still a crime novel.

My book is about a wedding photographer who has an affair with a guest that she met at a wedding, they is a story behind it but its quite graphic in places, whilst the story is very emotional and romantic in places as it tells the tale of how they became to be the people who they are and the events in their lives that shaped them as characters and how they got together. However that said the sex sceans are graphic and very discriptive.

I am personally not ofended by sexual language and nor are the people who have proof read it so far for me but in the same sence i couldnt see the BBC been able to use it as a script.

It never started been writen with the view to publish however I have had some exceptional feedback on it but i really dont know if they is a market for what i presume would be erotic chick lit x

I have sex scenes in some of my writing but I try to present it in a way that allows the reader to learn something about the character, otherwise it's just erotica. For example, I have a dark suit wearing amoral corporate worker on the make who is utterly selfish. The first time we meet him he is on the receiving end of a sexual act - nothing reciprocal at all. The description is brief and uncomfortable, but we learn a little about him as a person. I think if you keep the character in mind then you'll always be able to shy away from making it too graphic. Also, I saw one of those armchair psychologists on Oprah or one of those kinds of shows years ago and he was talking about affairs. One thing hs said stuck with me. "When people cheat it's rarely about the sex, it's about how the new partner makes them feel". I suspect your female character (I'm assuming it's a hetro affair) isn't "lying back and thinking of England", so what is she thinking about? Focus on how the sex act makes you characters feel rather than focussing on how the act itself feels.

If you try to write it without being graphic you might end up writing in trite euphamisms like "his manhood" etc, and that's just funny and best to be avoided